The present invention relates to a lubricating structure in a fixed displacement piston type compressor with a rotary valve that introduces fluid from a suction pressure region into a compression chamber in accordance with its rotation.
A piston type compressor disclosed in Unexamined Japanese Patent Publication No. 7-63165 employs a rotary valve for introducing refrigerant into a compression chamber defined in a cylinder bore. A double-headed piston in the compressor reciprocates by the rotation of a swash plate. In this fixed displacement swash plate type compressor, a rotary shaft itself functions as the rotary valve. In comparison to a flapper suction valve that opens and closes a suction port for introducing refrigerant into the compression chamber, a rotary valve improves volumetric efficiency.
The refrigerant containing lubricant oil in the compression chamber leaks through a gap between the piston and the inner circumferential surface of the cylinder bore into a crank chamber that accommodates the swash plate. An unwanted feature is that the refrigerant leaked into the crank chamber flows out to a suction pressure region along the circumferential surface of the rotary shaft. As a result, the lubricant oil in the crank chamber also flows out to the suction pressure region. Meanwhile, a shoe slides on the swash plate in the crank chamber to transmit the power of the swash plate to the piston so that the sliding portion needs to be lubricated. However, since the lubricant oil together with the refrigerant in the crank chamber flows out to the suction pressure region along the circumferential surface of the rotary shaft, the crank chamber cannot ensure the sufficient amount of lubricant oil. Therefore, it is desired that lubricating performance is improved in a fixed displacement piston type compressor with a rotary valve.